<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    const a=3.1415//a为只读常量,重复赋值会报错,声明的时候也必须同时赋值进行初始化
    // a=3.1415926
    console.log(a)
</script>
</html>